Actually, it's the creditors of a modern corporation who assume the risk. Shareholders have limited liability in almost all modern businesses. And that's without getting into government and central bank bailouts when things turn south.
And it's also false that shareholders necessarily have anything to do with financing the actual operations or plant of a company. I can become a shareholder in a company today by paying some money to an existing shareholder. I will then be entitled to a share of the profits despite doing absolutely nothing to contribute to creating the capital used by the company.
True, but how is it different? The point is that public companies would never allow risk. There would be not any facebook or uber.
How the job should be the only source of income? This sounds too medieval. But still, even this guy will get an another job. But the investments would be gone.And realistically speaking, the loss of a job, the only source of income, is typically a far greater risk for a worker than the loss of investment income from a firm is to someone who derives most or all of their income from owning assets.